Vaccination has proved to be one of the most effective means of preventing diseases, particularly infectious diseases. Most vaccines work by inducing antibodies that are protective against infection by the relevant pathogen. However many new vaccines target the cellular arm of the immune system and work by inducing effector and memory T cells. These can target intracellular pathogens and tumours. Many new T cell inducing vaccines that may be used either prophylactically or therapeutically are in development.
T cells induced by vaccination may be useful in various ways. As well as reducing risk of diseases in the vaccinee they may be used in adoptive transfer protocols to reduce risk of infection or disease in those receiving these cells. They may also be useful diagnostically.
An increasingly widely used method of inducing an immune response is to clone an antigen or epitope of interest into a vector. Vectors may be plasmid, bacterial or viral. Plasmid DNA vaccines are under intensive development and a variety of viral vectors appear useful for vaccination. These include poxviruses such as modified vaccinia virus Ankara (MVA), avipox vectors such as fowlpox and canarypox and ALVAC, herpesvirus vectors (including herpes simplex and CMV), alphaviruses and adenoviruses. There is increasing interest in the use of adenoviruses as vaccine vectors because of their ability to induce strong cellular and antibody responses.
Diseases that might be targeted by improved adenovirus vectors include but are not limited to malaria, tuberculosis, HIV/AIDS, HCV, HBV, HSV, HPV, CMV, diseases caused by encapsulated bacteria such as the pneumococcus, parasitic diseases such as leishmaniasis, and a wide range of tumours and cancers, such as lymphoma, leukaemias, melanoma, renal, breast, lung, prostate, pancreatic and colorectal cancers.